Parenting with Automatic Weights- Bone Heat Weight Failure
The main cause of that error is when there are overlapping/duplicate vertices and/or intersecting parts.

I would suggest a couple of things.

First, your model has a huge number of faces. 287k faces for an object like that is quite a lot. The large number of faces is making it hard for blender to tell which vertex should be assigned to which bone. I would suggest making the model with way less faces and using a Subdivision Surface modifier to make it smooth. Unfortunately that would me remaking your model but it will save you countless headaches in the future. Using the decimate modifier set to unsubdivide with 6 iterations can do most of the work for you, but it doesn't seem to work on the legs very well.

Second, automatic weights is not going to be the best way to rig your tripod. Your tripod is made of a number of segments and each segment looks like it should be parented to a single bone. Automatic weights will assign each vertex to the nearest bone(s) and thus you will have multiple bones controlling each segment and the segments will bend and deform. Instead, I would suggest parenting with empty groups and manually selecting each section of the tripod in edit mode and assigning it to the appropriate vertex group. Hovering your mouse over a vertex and pressing L will select everything connected to what is under your mouse which will save you time selecting each section.